AlGaN/GaN肖特基二极管阳极后退火界面态修复技术

Interface-state suppression of AlGaN/GaN Schottky barrier diodes with post-anode-annealing treatment

AlGaN/GaN异质结构材料在较强自发极化和压电极化的作用下,会产生高面密度和高迁移率的二维电子气,保障了基于该异质结构的GaN肖特基二极管器件具有高输出电流密度和低导通电阻特性.阳极作为GaN肖特基二极管的核心结构,对器件的开启电压、反向漏电、导通电阻、击穿电压等核心参数具有重要影响.因此,制备低界面态密度肖特基结是实现高性能GaN肖特基二极管的前提.本文基于低功函数金属钨阳极AlGaN/GaN肖特基二极管结构,通过采用阳极后退火技术促进阳极金属与下方GaN材料反应成键,有效抑制了阳极金-半界面的界面态密度,经阳极后退火处理后,器件阳极界面态密度由9.48×10^(15)eV^(-1)·cm^(-2)降低至1.77×10^(13)eV^(-1)·cm^(-2).得益于良好的阳极低界面态特性,反向偏置下,阳极隧穿路径被大幅度抑制,器件反向漏电降低了2个数量级.另外,器件正向导通过程中,载流子受界面陷阱态影响的输运机制也被抑制,器件微分导通电阻从17.05Ω·mm降低至12.57Ω·mm.实验结果表明,阳极后退火技术可以有效抑制阳极金-半界面态密度,大幅度提高GaN肖特基二极管的器件特性,是制备高性能GaN肖特基二极管器件的核心关键技术.

Owing to the high density and high mobility of two-dimensional electron gas(2DEG)induced by strong spontaneous polarization and piezoelectric polarization effect,AlGaN/GaN Schottky barrier diodes(SBDs)with high output current density and low on-resistance have proved to be a promising candidate.Anode of GaN SBD is the core structure,which affects the device performance such as turn-on voltage,reverse current,onresistance,and breakdown voltage.Therefore,idealized Schottky junction with low interface state density is very important in achieving high-performance GaN SBD.In this work,AlGaN/GaN SBD with low workfunction metal W as anode is fabricated,and the post-anode-annealing(PAA)treatment is found to be effective in promoting the bonding reaction between anode metal and GaN in the anode region.Comparing with GaN SBDs without PAA treatment,the interface state density decreases from 9.48×10^(15) eV^(−1)·cm^(−2) to 1.77×10^(13) eV^(−1)·cm^(−2) after PAA treatment.The reverse leakage current is reduced by two orders,which ascribes to the idealized anode interface with low interface state density.Meanwhile,the influence of interface state on carriers in the forward conduction process is also suppressed,and the differential on-resistance of the fabricated GaN SBDs decreases from 17.05 W·mm to 12.57 W·mm.It is obvious that the PAA process proves to be an effective method to suppress the interface states density at M/S interface,thus significantly improving the performance of GaN SBD,which is the key technology in fabricating the high-performance GaN device.